Conventionally, as an optical fiber sensor applied to a light sensing technology, an OTDR (Optical Time Domain Reflectrometer)-based optical fiber sensor which measures the physical quantity (such as temperature and loss) and a defect position in an optical fiber, by measuring a backscattering light caused by Rayleigh scattering which is generated while a light pulse is inputted into the optical fiber, has been known.
On the other hand, the shape of Brillouin gain spectrum (BGS) of Brillouin scattering light outputted from an optical fiber changes due to temperature and/or strain of the optical fiber. As a technology measuring the physical quantity of an object by using this change, a BOCDA (Brillouin Optical Correlation Domain Analysis)-type optical fiber sensor which has been described in, for example, patent document 1 and non-patent document 1 has been conventionally known.
Patent document 1: Japanese Patent Laid-Open Publication No. 2000-180265
Non-patent document 1: Kazuo Hotate, and Hiroshi Arai, “Enlargement of Measurement Range by a Temporal Gating Scheme in BOCDA Fiber-Optic Distributed Strain Sensing System with Time-Division Pump-Probe Generation Scheme”, IEICE Technical Report, The Institute of Electronics, Information and Communication Engineers, OPE2004-224 (2005-02)